The story of The Greatest Showman follows Jackman as P.T. Barnum through most of his life, and ends with him seemingly leaving the circus life behind, more or less, so it would appear that the story was complete, but if somebody found a reason to make a sequel, Jackman would certainly listen to the pitch.
While Hugh Jackman doesn’t elaborate on what “right thing to do” means exactly, we can probably safely assume he’s talking about a good script with a story worth telling.